Max Weight of Non Lift Producing Components

Well.....all I can say is, the EPA is a major US government agency, thus, likely quite large.
So, either eat a huge amount of oysters or renew your prescription for your "little blue pill of choice" as it may be borderline on screwing the whole agency......
YMMV.......
;-)

Whatever.....the basics of what I posted is correct (minus stupid side comments on my part). I'm really concerned on the physics. I believe I am correct.

I'm not an engineer.
I know a few.
I can spell it.
I have not stayed at a certain hotel chain in a couple years.

:-)
LOL......

At 22:44 30 November 2017, Bob Kuykendall wrote:
On Thursday, November 30, 2017 at 9:00:07 AM UTC-8, Kevin Neave wrote:

So what does the main pin(s) count as?

Very incisive question! That's a good demonstration of how the mass of
non-=
lifting is a reasonable metric for the approximation of wing main spar
maxi=
mum bending moment, but is still just an approximation.

At issue is that using a maximum mass of non-lifting parts to limit the
win=
g spar bending moment is only valid when any mass added to the wings is
dis=
tributed spanwise according to the wing lift distribution. So if for
whatev=
er reason you add a bunch of mass to the inboard ends of the wings
(deplete=
d uranium root ribs maybe?), you can be within the allowable non-lifting
ma=
ss and within the load factor envelope, but still develop excessive wing
sp=
ar bending moment.

Bottom line: Respect mass limits to the spirit and the letter of the
publis=
hed values. And if you want a glider with lots of non-lifting mass
margin,
=
build an HP-24. The one we finished last summer has an empty non-lifting
ma=
ss of ~220 lbs (ready to fly with batteries, instruments, 24 ft^2 O2
bottle=
, etc) and a maximum of ~605 lbs, yielding a payload of ~385 lbs for
pilot,=
parachute, FES, electric self-launch, BRS, etc.

--Bob K.

Ever wondered why commercial jets now all hang the engines from the wings?
Lighter spars and the added roll inertia in the wing component reduces the
effect of turbulence on the passengers.

On Thu, 30 Nov 2017 10:07:57 -0800, phouchg278 wrote:

Does anyone know, how exceeding that non-lifting weight influences the
flutter of the wing?

Its more a structural thing than load related.

Increasing surface torsional stiffness delays the onset of flutter and
putting the CG of the flying surface in front of the torsion axis damps
it out.


--
Martin | martin at
Gregorie | gregorie
| dot org

On Friday, December 1, 2017 at 3:44:44 AM UTC-8, Kiwi User wrote:
On Thu, 30 Nov 2017 10:07:57 -0800, phouchg278 wrote:

Does anyone know, how exceeding that non-lifting weight influences the
flutter of the wing?

Its more a structural thing than load related.


For the non engineers that might read this..... a loading illustration
using two examples:

Use a (really long)tongue depressor and white glue to glue a hollowed out eggshell to the half span point. Let it dry. Take a wing tip and do anything you like to shake the egg off the stick. Not enough mass in the eggshell to part it from the stick. Safe scenario = under max non-lifting parts weight.

The worst case scenario is the same eggshell full of heavy stuff. Mercury would be great - but its impractical. Imagine it. Load that egg (fiberglass shell) to the max, and then introduce a bunch of G's via centrifical or gust(rotor flight)force. The eggshell will rip off the stick(spar). Or, the stuff inside the shell will rupture it and leave the scene - think an over-max-payload person attached to max 242 lb. (110 kg) seat belt attaching points.

There are recurring discussions about how much margin designers provide for protection from this and that (max non lifting, Vne, gust loads, seatpan loads). My response is always - do you know the life history of this pretty fiberglass? The controlrod end play? The hingepoint tightness? How many times someone flew it how close to/over Vne due to an antique instrument or partially plugged pitot line? I am not in favor of flying beyond manufacturer's limits for anything.....
thanks for the many contributors to good info on this thread.

Cindy B

On Friday, December 1, 2017 at 10:00:14 AM UTC-8, CindyB wrote:

There are recurring discussions about how much margin
designers provide for protection from this and that...

One of the more high-profile examples is this RV-10 airplane for which the amateur builder arbitrarily increased the gross weight by a hundred pounds. Designer Dick Vangrunsven rightfully took issue with this practice:

https://www.facebook.com/notes/vans-...37594966250883

...I am not in favor of flying beyond manufacturer's limits for anything...

That's the best plan!

--Bob K.

On Friday, December 1, 2017 at 12:15:07 PM UTC+3, Jim White wrote:
At 22:44 30 November 2017, Bob Kuykendall wrote:
On Thursday, November 30, 2017 at 9:00:07 AM UTC-8, Kevin Neave wrote:

So what does the main pin(s) count as?

Very incisive question! That's a good demonstration of how the mass of
non-=
lifting is a reasonable metric for the approximation of wing main spar
maxi=
mum bending moment, but is still just an approximation.

At issue is that using a maximum mass of non-lifting parts to limit the
win=
g spar bending moment is only valid when any mass added to the wings is
dis=
tributed spanwise according to the wing lift distribution. So if for
whatev=
er reason you add a bunch of mass to the inboard ends of the wings
(deplete=
d uranium root ribs maybe?), you can be within the allowable non-lifting
ma=
ss and within the load factor envelope, but still develop excessive wing
sp=
ar bending moment.

Bottom line: Respect mass limits to the spirit and the letter of the
publis=
hed values. And if you want a glider with lots of non-lifting mass
margin,
=
build an HP-24. The one we finished last summer has an empty non-lifting
ma=
ss of ~220 lbs (ready to fly with batteries, instruments, 24 ft^2 O2
bottle=
, etc) and a maximum of ~605 lbs, yielding a payload of ~385 lbs for
pilot,=
parachute, FES, electric self-launch, BRS, etc.

--Bob K.

Ever wondered why commercial jets now all hang the engines from the wings?
Lighter spars and the added roll inertia in the wing component reduces the
effect of turbulence on the passengers.

Having them in front of the wing also acts as a mass balancer, counteracting flutter and turbulence. This is very obvious on the A380, which rides incredibly smoothly. (it also has a funky 3 outboard aileron setup, and they are CONSTANTLY moving rapidly, in different directions from each other, obviously under computer control)

I admit I am baffled by "max weight of non-lifting parts". I understand the issue of spar bending moment limits, and I think I understand that weighing a glider without its wings will give the current non-lifting (i.e., non-wing) weight, but I have a feeling there are subtle things here that I do not understand.

For example, the ASK-21 POH lists the following weights:

Empty weight: approx 780 lbs
Max all-up weight: 1320 lbs
Max weight on non
lift producing members: 902 lbs

I've rigged an ASK-21 and its wings are HEAVY! I haven't weighed them so I don't know just how heavy they are though. Certainly felt like more than 100 lbs each. Ask me how I know. I'll guess (I know, don't guess) each wing weighs 150 lbs. Likely more. If I subtract 300 lbs from 780 and then subtract that result from 1320 I'm still short of 902 - which I suppose is a good thing.

Oh well. This all just makes my head hurt. Maybe what I should be doing is adding the weight of pilots, water, parachutes, etc. to 780 to ensure that the total is not beyond 1320. I suppose I already do this when I use Foreflight to calculate W&B.

TIme for a nap.

On Thursday, December 7, 2017 at 7:27:02 PM UTC-5, Jim wrote:
I admit I am baffled by "max weight of non-lifting parts". I understand the issue of spar bending moment limits, and I think I understand that weighing a glider without its wings will give the current non-lifting (i.e., non-wing) weight, but I have a feeling there are subtle things here that I do not understand.

For example, the ASK-21 POH lists the following weights:

Empty weight: approx 780 lbs
Max all-up weight: 1320 lbs
Max weight on non
lift producing members: 902 lbs

I've rigged an ASK-21 and its wings are HEAVY! I haven't weighed them so I don't know just how heavy they are though. Certainly felt like more than 100 lbs each. Ask me how I know. I'll guess (I know, don't guess) each wing weighs 150 lbs. Likely more. If I subtract 300 lbs from 780 and then subtract that result from 1320 I'm still short of 902 - which I suppose is a good thing.

Oh well. This all just makes my head hurt. Maybe what I should be doing is adding the weight of pilots, water, parachutes, etc. to 780 to ensure that the total is not beyond 1320. I suppose I already do this when I use Foreflight to calculate W&B.

TIme for a nap.

1320-904=416 lbs. I'd guess closer to 180 per wing when you consider an ASG-29 wing weighs 140. Also, the horizontal stab and elevator are lifting. I don't know if you count the 22 lbs per wing root baggage compartment or not... I think that's lifting too. So, 360 lbs of wing, 44 lbs of baggage (worst case) which leaves about 12 lbs for tail bits.

On Thursday, December 7, 2017 at 6:27:02 PM UTC-6, Jim wrote:
I admit I am baffled by "max weight of non-lifting parts". I understand the issue of spar bending moment limits, and I think I understand that weighing a glider without its wings will give the current non-lifting (i.e., non-wing) weight, but I have a feeling there are subtle things here that I do not understand.

For example, the ASK-21 POH lists the following weights:

Empty weight: approx 780 lbs
Max all-up weight: 1320 lbs
Max weight on non
lift producing members: 902 lbs

I've rigged an ASK-21 and its wings are HEAVY! I haven't weighed them so I don't know just how heavy they are though. Certainly felt like more than 100 lbs each. Ask me how I know. I'll guess (I know, don't guess) each wing weighs 150 lbs. Likely more. If I subtract 300 lbs from 780 and then subtract that result from 1320 I'm still short of 902 - which I suppose is a good thing.

Oh well. This all just makes my head hurt. Maybe what I should be doing is adding the weight of pilots, water, parachutes, etc. to 780 to ensure that the total is not beyond 1320. I suppose I already do this when I use Foreflight to calculate W&B.

TIme for a nap.

Max weight of non-lifting parts;
Maybe it's listed that way to prevent the rationalization "the useful load is less than I want, I will use some of the water ballast allowable weight to justify excess pilot weight, and still be under max gross"

Nobody would do that would they? ;-)

On Thursday, December 7, 2017 at 5:59:55 PM UTC-8, Dan Daly wrote:
...Also, the horizontal stab and elevator are lifting.

I don't think that's the generally accepted interpretation. It is definitely not the interpretation I apply when I publish W&B data.

Yes, they produce lift, but in most (but not all) flight regimes it's downward, not up.

--Bob K.